The invention relates to load handling trolleys of the type that normally run in channel tracks and comprise elongate load engagers raisable and lowerable relative to bogies via ramp-and-roller means when the engager and the bogies are caused to move longitudinaly relative to each other. The trolleys are conveyed under a load, such as a pallet, in first a lowered state and are then raised to engage and lift the load for further conveyance.
Successful and well-known examples of such trolley-in-track systems are available from the applicants under the Registered Trade Mark JOLODA; and is set forth in U.S. Pat. No. 3,091,477.
A strong reasonably flat floor into which the tracks are laid, and reasonably rigid loads, such as containers or pallets, have led to remarkably lowprofile trolleys in quite shallow tracks as only a small lift height has been adequate to give a free travel clearance for the load over the floor after insertion of and raising the trolley.
There is now a tendency, dictated by seeking minimum costs of floors, pallets and containers, for floors to be less reliably strong and flat and for loads to be less rigid, so that flexing or sagging can result in previously satisfactory lifting heights being insufficient to avoid load-to-floor contact during movement of loads by the trolleys.
It is an object of this invention to provide trolleys with a higher lift height without requiring a deeper track and a higher profile for the trolleys in their unraised state.
The success and reputation of JOLODA trolleys is based on sound and well-engineered design involving, inter alia, close juxtaposition of the bogie side walls and the depending walls of the inverted channel section load engagers, virtually flush bottoms of such walls in the unraised state of the trolleys, and positive retention means between those side and depending walls. We further seek to be able to retain those features, but the limits set by rigid pin-and-ledge, groove or slot type positive retention means preclude achievement of desired amounts of increased lift.
Accordingly, we now propose a positive retention means that is basically characterised by including a device having one component that is anchored to the load engager and at least one other relative movable component connected to the first component and coupled to the bogie assembly so as to move during relative movement of the engager and bogie assembly.
It is evident that, for greater lift within the same basic trolley height, the ramp means must more nearly approach the available height of the space within the inverted channel type load engagers encompassing the bogies, though we prefer that it should remain slightly less so that positive lateral location of the sides of the bogies remain even when approaching and when at full lift height of the trolley. This result is due to overlap by the depending sides of the load engager, which are preferably closely adjacent thereto throughout their length. Lift height will usually be greater on approach if, as is preferred, the ramps have locating depressions at full height.
A particularly robust embodiment has retention means in the form of spring links engaging and effectively in guiding/retaining engagement with rollers or some other cross-connection of the bogies, say encompassing axles or rods thereof in a slot of the links otherwise anchored, say clamped under wedges with which the rollers coact.